About kerning and tracking (6.5)

You can automatically kern type using metrics kerning or optical kerning. Metrics kerning uses kern pairs, which are included with most fonts. Kern pairs contain information about the spacing of specific pairs of letters such as LA, To, Tr, Ta, Tu, Te, Ty, Wa, WA, We, Wo, Ya, and Yo. After Effects uses metrics kerning by default so that specific pairs are automatically kerned when you import or type text.

Some fonts include robust kern-pair specifications. For other fonts, or for two different typefaces or sizes in a line, you may want to use the optical kerning option. Optical kerning adjusts the spacing between adjacent characters based on their shapes. You can also use manual kerning, which is ideal for adjusting the space between two letters. Tracking and manual kerning are cumulative, so you can first adjust individual pairs of letters and then tighten or loosen a block of text without affecting the relative kerning of the letter pairs.

Note: Values for kerning and tracking affect Japanese text, but normally these options are used to adjust the aki between roman characters.