This note surveys the definition of quasilocal mass and its positivity. In particular, we focus on Brown-York and Liu-Yau quasilocal mass. We first present Shi and Tam''s result on the positivity of quasilocal mass in the Riemannian case and then Liu and Yau''s approach to the general case. Finally, we mention a modification of Liu-Yau quasilocal mass by Wang and Yau.
