Verb

Verbs Express Actions
Verbs are doing words. A verb can express:
A physical action (e.g., to swim, to write, to climb).
A mental action (e.g., to think, to guess, to consider).
A state of being (e.g., to be, to exist, to appear).

Lots of Verbs Express Physical Actions
Here are some sentences with the verbs highlighted. (These verbs express physical actions.)

She sells pegs and lucky heather.
(In this example, the word sells is a verb. It expresses the physical activity to sell.)
The doctor wrote the prescription.
(In this example, the word wrote is a verb. It expresses the physical activity to write.)
Alison bought a ticket.
(The word bought is a verb. It expresses the physical activity to buy.)
Verbs Express Mental Actions Too
As we covered at the start, verbs do not necessarily express physical actions like the ones above. They can express mental actions too:

Example:
She considers the job done.
(The word considers is a verb. It expresses the mental activity to consider.)
Peter guessed the right number.
(The word guessed is a verb. It expresses the mental activity to guess.)
I thought the same thing.
(The word thought is a verb. It expresses the mental activity to think.)

Verbs Express a State of Being
A small, but extremely important group of verbs do not express any activity at all. The most important verb in this group – arguably of all – is the verb to be. As already mentioned, this is seen in forms like is, are, were, was, will be, etc.