英语有句话不懂,People are bound within relationships by two types o

英语有句话不懂,
People are bound within relationships by two types of bonds:expressive ties and instrumental ties.Expressive ties are social links formed when we emotionally invest ourselves in and commit ourselves to other people.Through association with people who are meaningful to us,we achieve a sense of security,love,acceptance,companionship,and personal worth.Instrumental ties are social links formed when we cooperate with other people to achieve some goal.Occasionally,this may mean working with instead of against competitors.More often,we simply cooperate with others to reach some end without endowing the relationship with any larger significance.
我不懂得是 Expressive ties are social links formed when we emotionally invest ourselves in and commit ourselves to other people.这一句
这里 invest in 和 commit to 是什么用法?
顺便说一句 不要给我翻译软件的答案，

表达性联系是一种社交性联系,它是当我们全心地去付出,同时也对别人付出时形成的.
invest in 是投入付出
commit to 是对sb、sth负责
这是两个并列的动词词组,当动词用.这里的and是个并列连词.

回答的不错