This is the 103rd most frequent Korean word.
것도
"것도" means "that too" or "also that" in English.
것도 is used to indicate 'also' or 'as well' when linking multiple items being consumed.
저녁으로 피자도 먹고 치킨 것도 먹었어요.
For dinner, I ate both pizza and chicken.
것도 emphasizes an additional aspect of the difficulty, showing how the speaker feels about the activity.
공부도 힘들고 공부한 것을도 잊어버렸어요.
Studying is hard, and I also forgot what I studied.
것도 is used to emphasize 'also' in combination with enjoying activities.