A verb that is not an auxiliary verb, is called an independent verb.
In general, a phrase has exactly one independent verb. This verb is used to specify the action of the sentence.
If there are any other verbs, those are auxiliary verbs. These verbs are used to indicate when or how the specified action takes place (presently, in the future, voluntarily, compulsory, possibly, etc.).
The auxiliary verb(s) is in _italics_, the independent verb bold.
Ik eet een broodje. | I eat a sandwich.
Ik _zal_ een broodje eten. | I _will_ eat a sandwich.
Ik _zal_ altijd broodjes _blijven_ eten. | I _will keep_ eating sandwiches forever.
In the last example, _zal_ (or will) is the auxiliary verb for _blijven_ (or keep), which is in turn an auxiliary verb for _eten_ (or eating). In the second example, _zal_ (or will) is the auxiliary verb for _eten_ (or eat)
It should be clear that an auxiliary verb can also function as an independent verb:
Ik wil een ijsje. | I want an ice cream.
Ik _wil_ een ijsje eten. | I _would like_ to eat an ice cream.
Ik _zou_ dat willen. | I _would_ like that.
ik _wil_ slapen. | I _want_ to sleep.
The verb _willen_ serves as an independent verb in the first and third example but it is an auxiliary verb in the second and fourth example (supporting _eten_ and _slapen_).
In general, the independent verb follows after the auxiliary verbs. You can also place it before an auxiliary verb, but this is not always allowed.
Four types of auxiliary verbs
We can distinguish four main types of auxiliary verb constructions:
- auxiliary verb + past participle
- auxiliary verb + _te_ \+ infinitive
- auxiliary verb + bare infinitive
- auxiliary verb + _aan het_ \+ infinitive
In the following sections, each type will be discussed. Unfortunately, each type has its own sub-types. A lot of reading, but once you have read it all, you know all possible types of auxiliary verbs.