in the context of infinitives, 'to' is a preposition that is used in conjunction with the base form of a verb (e.g., to run, to eat, to think). This combination is known as the 'to-infinitive' and serves various functions in sentences, including expressing purpose, intention, or a subsequent action.
the 'to-infinitive' is used after many main verbs (e.g., 'I want to go home'). It can express purpose or reason (e.g., 'She studies hard to pass the exam'). It can follow adjectives to provide a reason for the adjective (e.g., 'I'm happy to help'). It can be used after certain nouns to indicate a related action (e.g., 'She has the ability to sing beautifully').
I decided to visit my grandmother next weekend.
He seems to understand the situation.
It's important to drink water regularly.
Not all verbs are followed by the 'to-infinitive'. Some verbs are followed by the '-ing' form (gerund) instead. For instance, 'I enjoy reading' (not 'I enjoy to read'). Some verbs can be followed by either the 'to-infinitive' or the '-ing' form with a change in meaning. For example, 'I remembered to do my homework' (I remembered that I needed to do it and so I did it) vs. 'I remembered doing my homework' (I have a memory of doing it). Avoid the double 'to' mistake. For instance, 'I want to to go there' is incorrect. It should be 'I want to go there'.