If fine vertical lines above your lip bother you and you have never booked a treatment, here is where they come from, in plain words.
Where the lines come from
my.clevelandclinic.org says the underlying cause is activity of the muscle around the mouth, which becomes more active with time. That is the whole answer in one sentence, and it is a good place to start before you look at any treatment.
Free reading before you spend a dollar
Reading costs nothing, so begin there. my.clevelandclinic.org has a page on lip lines, their causes and the filler and other treatments used that puts the topic in one place. An article on perioral rejuvenation by minimally invasive procedures covers the area around the mouth from the clinical side.
If filler comes up, two sources are worth a look first. One is an injectables overview and the other is the FDA page on soft tissue fillers.
The cheap step and the step that is not yours to take
The cheap step is to write down when you first noticed the lines and what bothers you most. That costs nothing and gives a clinician something concrete to work from. Choosing and giving a treatment is not a do-it-yourself matter, so leave injectables to a licensed professional.
Bring the question to a clinician
You do not need to know the right words to book a first visit. Ask a licensed clinician what is causing your lines and what, if anything, fits your budget. A plain question is enough to begin.