“DDR3” = third-generation memory with 240 pins (desktop) or 204 pins (laptop) depending on form factor.
“8 GB” = capacity.
“PC3-xxxx” = expected memory bandwidth classification.
“1800p” = indicates a roughly 1800 MT/s data rate, which in practice is similar in performance to standard DDR3-1866 speeds (often tagged PC3-14900)