FPGA’s contain Block RAM (BRAM) & Distributed RAMs (DRAM). BRAM’s are dedicated memory blocks. Each FPGA has them. FPGA datasheets typically specify the Total BRAM in Kbits. 

DRAM’s are RAM’s that can be constructed using Look-Up-Tables (LUT). 

SRAM based FPGA’s have LUTs. These LUTs can be used as a small block of RAM by combining cells; called DRAMs.

This kind of RAM is called DISTRIBUTED as LUTs are or spread out across the FPGA fabric. 

- This post is inspired from Clive “Max” Maxfield book on FPGA’s