Kerry, your questions are too general for us to be able to give you full answers here. You need to do some research preparation. Look up the terms you've mentioned at:

www.webopedia.com

and then follow up by using Google to search for further information. Use search terms like "What is SDRAM" or "how to choose RAM" and spend some time looking through the results for discussion articles.

Let us know the exact make and model of your computer (or your motherboard) and we will be able to help with more specific questions. For now, though:

Yes, the memory slots on your motherboard are for your RAM, and there are different types of slots for different types of RAM module. you need to get the type which suits your motherboard.

IDE connectors are the plugs on the data cable for your hard drives and CD/DVD drives.