GRAMMAR, PLAINLY.
SENTENCES → QUESTIONS · RULE 12

Questions

To ask, English puts a helper word before the subject: do, does or did. The main verb goes back to its base form.

FORMULA
do / does / did
YES / NO QUESTION
Does
HELPER
she
SUBJECT
walk
VERB — BASE
to work?
WH- QUESTION
Where
WH-WORD
does
HELPER
she
SUBJECT
work?
VERB — BASE
THREE KINDS
?
Does she walk to work?
Does + subject + V1
Wh
Where does she work?
wh-word goes first
be
Is she at work?
be just flips — no helper
The helper carries the tense: does = present, did = past. So the main verb stays simple: Did she go?
PICK THE HELPER
I / you / we / theydoDo they know?
he / she / itdoesDoes it work?
everyone in the pastdidDid you call?
NO HELPER NEEDED
with beAre you tired? Was it good?
with can · will · mustCan she swim? Will they come?
who as the subjectWho called you?
COMMON MISTAKES
Does she walks?→ Does she walk?after does — base verb
Where she works?→ Where does she work?questions need the helper
Did you went home?→ Did you go home?after did — base verb