If something tends to happen, it usually happens or it often happens.

If you tend towards a particular characteristic, you often display that characteristic.

You can say that you tend to think something when you want to give your opinion, but do not want it to seem too forceful or definite.

If you tend someone or something, you do what is necessary to keep them in a good condition or to improve their condition.

If you tend to someone or something, you pay attention to them and deal with their problems and needs.