What is vcc?

Some articles on vcc:

Serial Presence Detect - Stored Information - SDR SDRAM
... Interface voltage level of this assembly (not the same as Vcc supply voltage) (0–4) Decoded by table lookup 9 0x09 Nanoseconds (0–15) Tenths of nanoseconds (0.0–0.9) Clock cycle time at ... Addr Buffered Addr Memory module feature bitmap 22 0x16 — — Upper Vcc (supply voltage) tolerance Lower Vcc (supply voltage) tolerance Write/​1 Read Burst Precharge ...