1. 插补文字;插入文字
An interpolation is an addition to a piece of writing.

1. the action of interjecting or interposing an action or remark that interrupts

Synonym: interjectioninterpositioninterpellation

2. (mathematics) calculation of the value of a function between the values already known

3. a message (spoken or written) that is introduced or inserted

e.g. with the help of his friend's interpolations his story was eventually told
with many insertions in the margins

Synonym: insertion