A more thorough explanation:

Fine capiendo pro terris was a legal document that allowed a person who was imprisoned for a crime to be released from jail and to recover their lands and goods that were taken during their imprisonment.

For example, if someone was arrested for a crime and their property was seized by the authorities, they could use fine capiendo pro terris to get their property back once they were released from jail. This writ was only available to felons who had been imprisoned for a certain period of time and who had property that was taken during their imprisonment.