this year是指这年，last year就是去年，例如
Covid 19 pandemic stated last year, but this year everyone on earth are still suffering. Over 4 millions people lost their lives. We have to get effective vaccination to overcome this virus and win the most battle. 新冠肺炎大流行是去年开始，但是今年全世界的人还在受苦，已经有超过4百万人失去生命，我们必须要有有效的疫苗才能克服病毒，取得胜利。
this year是“今年”的意思，
last year是“去年”的意思。
