When a part is played into a sequencer or DAW, the notes rarely land exactly on the beat. Quantizing moves them towards the nearest point of a chosen grid, such as eighth or sixteenth notes. Most software lets the producer apply it partially, with a strength setting that moves notes only part of the way, and can add swing at the same time. In Logic Pro, as in many DAWs, quantizing MIDI is non-destructive, so the original performance can be restored.
Roger Linn introduced timing correction together with adjustable swing on his LM-1 Drum Computer at the turn of the 1980s. In his scheme a swing value of 50% means straight time and about 66% gives a full triplet feel, with subtle shades in between. Jazz lo-fi producers often quantize lightly, or not at all, to keep the human looseness that suits the style.