The next thing is the one after this one.
I saw her again the next day.

The advances in technology will be amazing in the next decade or so.

When this is completed, the next step will be to edit everything carefully.

She plans to leave the company in the next two years.
The next place is the one beside, or on the other side of this one.
No, this is number 12, number 14 is the next house.

Be quiet, the children are sleeping in the next room.
Next week, month, year, etc. is the one that follows this one.
I'll see you again next week.
Next is used with a superlative adjective to denote what follows in the specified order.
The next best thing to flying is gliding.

Preposition

After something in order.
Next, we have the 6:00 news.
The time after this one.
The woman was next seen in the office 4 days later.

It was performed next the following year.
Beside something.
She stood next to the window.

next