You can use forms to directly trigger Actions either through buttons or through various form events (such as form opening, saving or closing).

NOTE: here we are talking about actions configured in Actions component, which offer a variety of backend processes, such as creating new items, printing, setting permissions, etc. Not to be confused with action buttons on the form, which can only set column values on the current form.

There are two ways to trigger an action on the form:

1. Button with Trigger action type selected. It can be used to trigger any action. Users have to click on the button to execute the action.
2. Form events (Item is added, Item is modified, Form is opened, Form is closed) - action is triggered automatically. Note that for action to be available for form events, it must have no events set in the action settings themselves, to prevent actions from being triggered twice.
   1. Item is added - action is triggered following a successful save of a new item.
   2. Item is modified - action is triggered following a success update of an existing item.
   3. Form is opened - Edit or Display forms are opened (doesn't work with New forms)
   4. Form is closed - form is closed using Cancel or Close button, not triggered when item is saved.

Actions can be triggered from the form for a variety of reasons:

1. If your list undergoes frequent updates (especially through other actions or workflows), actions might get throttled when executed on event. Executing them on forms only ensures they are only triggered when items are actually updated by users.
2. Action needs to be triggered of events not supported through regular list events (such as form opened or closed).
3. Action is manual and users are allowed to decide when to run a particular action.

NOTE: action triggered through form always execute under administrative permissions, regardless of the action settings (with or without Impersonation). Additionally, "after change" conditions are currently treated as "always" condition. 

For each event type or button, you can only trigger a single action. If you want to execute a set of actions, use an Action Group and trigger that group instead.