When your package still says in transit it often means that the package is still being transported and is on a truck going down the road.
Or the package may have arrived at the sorting facility but has not yet been scanned.
The packages only get scanned when they arrive at a sorting facility or post office and don't get scanned while on the truck being transported.
Packages can stay in transit for a few days in some cases before being scanned at a sorting facility.
USPS, UPS and FedEx transport and sort millions upon millions of packages and it can take some time to get to your package and scan it.
You shouldn't worry about the package still staying in transit unless it's been longer than 3 days.
In most cases the tracking on your package will update from in transit within a day or two.
Your package may be experiencing a delay in getting to the sorting facility such as through problems such as weather or mechanical breakdown of the trucks or there's a delay at the sorting facility due to high volume, staff shortages or system outages.
Mis sorted packages, delays in flights/trucks and rerouting can also cause unexpected delays in shipping of packages.
In transit basically means that your package is on it's way to you and it does not always mean that the package is moving in a vehicle or aircraft and it may even be at the sorting facility.
A package can stay in transit for 24 hours to 7-9 days depending on the service and route.