Memory Type: DDR2 PC2-5300, DDR2 (non-ECC)
Maximum Memory: 2GB
17-inch 1.83GHz Intel Core Duo (MA199LL) and 20-inch 2.0GHz Intel Core Duo (MA200LL)
Memory or DRAM is the "working" memory of the computer. It's used to store data for programs (sequences of instructions) on a temporary basis.
Install Guide for your:
iMac (Early 2006)
video - installing memory