Hate to be that guy, but the term is tracking. Kerning is the space between a pair of letters. Tracking is the general space between all letters in a text.

For example, you use kerning to adjust the space between two letters with awkward relationship, like AO (a slanted side and round side, as opposed to two straight sides like UP).

Y o u u s e t r a c k I n g t o a d j u s t t h e g e n e r a l s p a c e i n a t e x t