Just has several meanings.
When used with a verb, just indicates the immediate past.
They have just gone. (= They went a very short time ago.)
She just phoned. (= She phoned a very short time ago.)
‘Where is the file?’ ‘I’m just bringing it.’ (= immediately)
I saw him just last week. (= I saw him as recently as last week.)
Just now can mean ‘at the moment’ or ‘a few seconds ago’.
She is not in just now. (= She is not in at the moment.)
I saw James just now. (= I saw James a few seconds ago.)
I am busy just now. (= I am busy at the moment.)
Just can mean ‘only’.
I just want some rest.
I just want a place to sit down.
I just want something to drink.
I just want somebody to understand me.
I just want a good job.
Just can also mean scarcely or almost not. This meaning is often emphasized with only.
We only just caught the train.
Just can mean exactly.
It’s just 2 o’clock. (= It is exactly 2 o’clock.)
That’s just what I meant. (= That is exactly what I meant.)
Just as an emphasizer
Just can be used to emphasize other words and expressions. It means ‘simply’.
You are just beautiful.
I just love the way she smiles.
When just means a moment ago, it is usually used with the present perfect tense in British English. In American English, a simple past tense is more common.
They have just arrived. (GB)
They just arrived. (US)