This is the 418th most frequent Polish word.
ich
"Their" or "them" (possessive or object pronoun).
In this sentence, 'ich' is used as a pronoun meaning 'them,' referring to a group of people in the objective case.
Widziałem ich na zajęciach wczoraj.
I saw them in class yesterday.
Here, 'ich' functions as a possessive pronoun in plural form, meaning 'their,' to indicate ownership of the plan.
To jest ich plan na weekend.
This is their plan for the weekend.
In this context, 'ich' is again a possessive pronoun referring to 'their,' this time describing the life belonging to the group in question.