Laitue vs. salade

The French words 'laitue' and 'salade' both relate to lettuce, but they are used differently in various contexts.

Laitue

'Laitue' specifically refers to the leafy green vegetable known as lettuce. It is a type of plant.
J'ai acheté une laitue au marché.
(I bought a lettuce at the market.)
La laitue est riche en fibres.
(Lettuce is rich in fiber.)
Nous cultivons des laitues dans notre jardin.
(We grow lettuces in our garden.)

Salade

'Salade' can refer to the plant itself (like 'laitue'), but it more commonly means a prepared dish that often includes lettuce as one of its ingredients.
Je mange de la salade tous les jours.
(I eat salad every day.)
Cette salade comprend des tomates, des concombres et de la laitue.
(This salad includes tomatoes, cucumbers, and lettuce.)
Voulez-vous une salade avec votre repas?
(Would you like a salad with your meal?)

Summary

'Laitue' generally refers to the raw vegetable known as lettuce, whereas 'salade' usually implies a prepared dish that includes various ingredients, potentially including lettuce.