WS-C2960-24TC-L vs WS-C2960-48TC-L

I want to buy cisco c2960 series switch which support voice, video, data, and highly secure access. My friend suggest me try to use WS-C2960-24TC-L or WS-C2960-48TC-L which are equipped with Ethernet 10/100 ports and 2 dual-purpose uplinks. But i don't know what's the difference between them ?