Insert effect
An effect patched directly into a channel's signal path, so the entire signal passes through it.
The alternative is an aux send, which routes a copy of the signal to a shared effect and blends the result back in. An insert replaces the original instead: what comes out is all there is. That is why compressors, EQ and noise gates belong here — half-compressed vocals are rarely what anyone wants. Reverb and delay usually go on sends so that many channels share the same room.
On analogue desks the insert point is often a single TRS jack, tip for send and ring for return. In a DAW it is the plugin slots in the channel strip, and their order matters: EQ before compression sounds different from the reverse.