In Salesforce there is a particular order in which events execute whenever a record is changed or inserted. Following are the steps of trigger execution:

Step 1:

Load the original record or initialize on insert.

Step 2:

Override the old record values with the new values.

Step 3:

Execute all before triggers.

Step 4:

Run the system & user-defined validation rules.

Step 5:

Save the record but do not commit the record to the database.

Step 6:

Execute all after triggers.

Step 7:

Execute the assignment rules.

Step 8:

Execute the auto-response rules.

Step 9:

Execute the workflow rules.

Step 10:

If there are workflow field updates then execute the field update.

Step 11:

If the record was updated with a workflow field update then execute before and after triggers created on the object in the context again but only once.

Step 12:

Execute the processes on that record.

Step 13:

Execute the escalation rules.

Step 14:

Update the roll up summary fields & cross object formula fields.

Step 15:

Repeat the same process with the affected parent or grand-parent records.

Step 16:

Evaluate criteria based sharing rules.

Step 17:

Commit all DML operations to the database.

Step 18:

Execute post commit logic such as sending emails.