Learn Swedish: Kameran är lagad nu. - The camera is repaired now.

In this sentence, the word lagad is a past participle. A past participle is formed from a verb (here, att laga) but is used like an adjective to describe the state of something. We are describing the camera as being in a repaired state, not saying that it did an action in the past.

Why does lagad end in -d?

Because it is acting as an adjective, it has to agree with the noun it describes. Kamera is an en-word, which we can tell from its definite form kameran. For en-words, the past participle of this verb group ends in -d. If we were describing an ett-word, like fönstret (the window), it would be fönstret är lagat.

Could I say Kameran har lagat nu instead?

No, that would mean the camera has repaired something itself! When you use har plus the verb form lagat, it describes an active action. Using är plus the past participle lagad describes the passive state the camera is currently in.

I thought laga meant to cook. Why does it mean repaired here?

The verb att laga is used for both cooking (usually as laga mat) and repairing or fixing things. You have to rely on context to tell them apart. Since cooking a camera does not make much sense, it means repaired here!