Toning, or toned black and white: toning images allows an artist/printer to alter the colours of a photographic print (by replacing the silver in the silver salts with another metal). Toning can be used as an aesthetic decision by the artist, or it can also be used to improve the archival properties of a print.
Titing, a process similar to toning, but involving the addition of a single colour over the whole print. The effect is most visible in the image's highlights and mid-tones. Used purely for aesthetic reasons, tinting does not affect a print's archival properties.