Just is a common adverb in English, especially in speaking. It has different meanings.
Just meaning ‘simply’ or ‘absolutely’
We can use just meaning ‘simply’ or ‘absolutely’ to add emphasis to a statement:
It’s just not right.
Our holiday was just perfect.
Just meaning ‘exactly’
You look just like your sister.
Can you put your signature just here?
Just meaning ‘only’
His first pay cheque was just fifty pounds.
[in a clothes shop]
Can I help you?B:
No, it’s all right, thanks. I’m just looking.
Just and expressions of time
Just can mean ‘recently’ or ‘a very short time before or after speaking’:
Where’s my phone? I had it just now.
Could you wait for me? I’m just going to the shop.
We often use the present perfect or past perfect with this meaning of just when we refer to a short time before the moment of speaking:
I’ve just decided to sell my apartment.
I’m on my way to the station. Their train has just arrived.
Just for emphasis
We also use just to emphasise an imperative:
Just shut the door quickly or we’re going to be late.
Just to soften expressions
We use just in speaking to soften what we say, especially in requests:
Could you just open the window?
I was just wondering if I could speak to you about Anna?