So starting with cpu basics. Intel stuff has higher ipc over AMD which basically means that each core individually is faster then an AMD at the same clock speed. So a 4th generation I5 from intel might have 10-25% faster per core performance over the equivalent AMD clocked parts. So AMD makes up for this with having a higher clock speed on each core and having more cores. An AMD Fx 8350 is clocked at 4ghz stock to help make it more competitive with an Intel I5 4690k which is clocked at 3.5ghz. Because the AMD has a higher clock, it can somewhat compete core to core with the I5 core to core although the Intel does win out because it has that much better ipc.
Ram is an easier to figure out piece. The clock speed is how fast the ram refreshes. For example DDR3 has common clock speeds of about 1600mhz to 2400mhz. Higher is available but not really common. DDR4 ram has common clock speeds of 2133mhz to 3000mhz. Cas Latency is basically how many refreshes the ram has to go through before it can produce a piece of information from the ram. So basically, the higher the mhz and the lower the cas latency, the better. Although really ram is one of the pieces in the system that doesn't affect gaming performance at all, although for stuff like editing and rendering it has a tiny boost.
Cpu coolers are another kind of glossed over piece. The bigger fans and heat sink the better. For a low cost option, go for a Hyper 212 evo. For a medium priced option go for a noctua nd-h15. For a higher end system go for something like the Corsair h100i gtx. If you want a part in between the 212 evo and nd-h15, go for the biggest noctua cooler you can fit.
Motherboards are a complicated one. Sata ports are your hard drive plug ins'. M.2 ports are higher speed hard drive plug in ports. M.2 ports connect more directly to the system then sata ports do and have more available bandwidth. Pcie lanes are you plug-ins for expansion cards. The more lanes available to a card, the better after a certain point. Basically 8x lanes are your lowest recommended bandwidth to a graphics card. Whether its a 8x pcie lane in generation 2 or 3, its probably not going to have any affect on the performance of a graphics card. A generation 2 lane has half the bandwidth of a generation 3 lane. So your 16x pcie 2.0 slot has equivalent bandwidth available to the graphics card as a 8x pcie 3.0 slot. In general on motherboards a newer generation chipset is better then an old one although sometimes chipset generations don't make that much of a difference. Intel's 8 series chipset to 9 series was pretty mehh.
Hard drives are a simple one. Solid State Drives, or SSD's, are faster then traditional spinning platter Hard Drives, or HDD's. The more gigabytes of storage the better and higher max sequential Mbs read and write is better. IOPS are another measure of read and write performance under a variation of conditions. Same as Mbs, higher is better.
Graphics cards. This is the fun one. So basically cuda cores and stream processors are the name of the compute cores on Nvidia and AMD graphics cards. For the both the AMD and Nvidia lineup of cards, just get the most expensive one you can afford with your system. Graphics cards are the most important piece for a gaming computer. More stream and Cuda cores are better, although that is somewhat locked to an architecture of cards. So like a Gtx 780 has 600 some more cuda then the 980, but the 980 is a good 25% faster or more. The cuda cores on the 980 are just individually much faster. For AMD the story isn't really the same. AMD has just been adding more stream processing cores rather then making every stream processing core faster and having less of them. That coupled with there cores not being as efficient is why there cards need more power then the newest Nvidia. More memory is better although for the next couple years 4-6gbs is the max you'll realistically need. Although if its a 960, r9 270/x, or lower tier card, don't bother with more then 2gb's. Vendors try to make an extra dollar by charging extra for those lower end cards with more ram then they have the horse power to use. A gt 430 can't dream of using 4gb's of v-ram but a vendor will try to sell ya one that has that much ram.
Power supplies are something that I'll run over but I never recommend buying one without consulting at least a couple older forum members. Basically you want at least 80+ bronze with a little bit of headroom for your system. It needs to be a good brand like Corsair, Seasonic, Evga, XFX, Silverstone, and a couple more. But even among those brands there are some stinkers even with higher then 80+ gold certification so make sure you always double check a psu selection with some long time members of forums. Power Supplies are something that you have to be active in the various tech communities to really keep on top of. People recommend builds using power supplies that are as close to bomb status as possible without knowing it most of the time.