der Lacher
gag / laugh
A remark, action, or situation that makes other people laugh.
Sein Versprecher am Ende der Rede war der größte Lacher des Abends.
His slip of the tongue at the end of the speech was the biggest laugh of the evening.

laugh / gag
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gag / laugh
A remark, action, or situation that makes other people laugh.
Sein Versprecher am Ende der Rede war der größte Lacher des Abends.
His slip of the tongue at the end of the speech was the biggest laugh of the evening.

'Der Lacher' is derived directly from the verb 'lachen' (to laugh). The ending '-er' turns the action into a noun that describes either the result (laughter) or the cause of the laughter.
Der Witz war gut, aber der eigentliche Lacher kam erst danach.
The joke was good, but the real laugh came only afterward.
You distinguish the meanings through context: when it is about the cause, it is often 'ein Lacher' (a laugh/gag). When it is about the sound, it is often described with adjectives like 'laut' (loud) or 'herzlich' (hearty).
Sein Kommentar sollte ein Witz sein, war aber kein großer Lacher.
His comment was meant to be a joke, but it wasn't much of a laugh.
In the meaning of 'something that makes people laugh', the word is often used in fixed combinations, such as 'für einen Lacher sorgen' (to get a laugh) or 'ein Riesenlacher sein' (to be a huge laugh).
Der Komiker sorgte mit seiner Geschichte für viele Lacher im Publikum.
The comedian got many laughs from the audience with his story.
The expression 'die Lacher auf seiner Seite haben' (to have the laughs on one's side) is fixed. Only the possessive pronoun ('seiner', 'ihrer', 'meiner') changes depending on the person.
Nach dem ersten Witz hatte die Rednerin die Lacher auf ihrer Seite.
After the first joke, the speaker had the laughs on her side.
joke
'der Witz' and 'der Lacher' are both connected with laughter. A 'Witz' is usually the content someone tells so that others laugh. A 'Lacher' is more something that triggers laughter, or the laughter itself. For example, you can say that a sentence was 'ein großer Lacher' (a big laugh / a big hit) if many people laughed about it. The words can be confused because a good joke is often a 'Lacher'. 'Witz' describes more the form, while 'Lacher' describes more the effect.

Lukas hat mit seiner spontanen Antwort den größten Lacher des Abends bekommen.
Lukas got the biggest laugh of the evening with his spontaneous answer.
Heute hat mir meine Schwester einen Witz erzählt, den ich sofort weitererzählen wollte.
Today my sister told me a joke that I immediately wanted to retell.