What is buffer size?
How many samples the audio interface processes per cycle. Small buffers reduce monitoring latency for the singer and raise CPU load; large buffers do the opposite and suit mixing rather than tracking.
Tracking vocals usually means a small buffer, so anything that adds no processing load is worth keeping in the session.
The delay between audio entering a system and leaving it, introduced by buffering and by processing. Plugins that do not process audio, such as a lyrics display, report no additional latency.
A digital audio workstation: the software you record, edit and mix in. Cubase, Logic Pro, Ableton Live, Pro Tools, FL Studio, Studio One, Reaper and Cakewalk are the ones most vocal sessions run on.