Some people still have the out-dated white plastic kind, which is not up to code.
The white plastic ducting is flammable. It should be shiny foil or best, solid metal ducting in case of a dryer fire.
You can also wrap the duct in insulation to improve efficiency (especially if the duct is more than 10ft long).
Ducts should be sealed at any seams or joints with FOIL tape NOT DUCT TAPE.
Duct tape has thousands of uses unfortunately none of which are actually ducting. So it is not very aptly named tape.
Foil tape has better adhesives and won’t dry out and fall off like duct tape does (making you do the same job twice).