to work
The French word 'travailler' is used similar to the English verb 'to work'. It can refer to a job or work action, and can be used in various contexts. For example, 'Je travaille dans une banque' means 'I work in a bank'. Like English, it can be conjugated in different tenses to indicate when the work is/was/will be done.
I must work harder.
This sentence explains a duty or an obligation to work harder. 'Dois' is the first person present of the verb 'devoir' which means 'must'.
He likes working with wood.
In this sentence, 'travailler' is used to express working with a specific material, in this case — 'wood'. 'Aime' is the third person present of the verb 'aimer' which means 'likes'.
We are going to work together.
This is an illustration of using 'travailler' to mean working cooperatively with others. The sentence structure '(subject + aller + infinitive verb)' is used to express a future action.