As far as I've gleaned from various sources over the years:

Chemtrails are seen when jet contrails fail to disperse after a few seconds. The wind at 6-7 miles is continuous and the usual water vapor clouds would normally clear up. Jet trails that remain visible for 20 minutes or longer usually contain aerosolized chemicals.

Chemtrails may be for the purpose of: meteorological research; outright cloud seeding for rain; the attempt to disperse agriculturally active chemicals into the atmosphere that wind up landing on crops and the ground.

Nobody officially in gov has ever admitted to producing chemtrails deliberately.

IMO: They probably exist but they are so clandestine (like everything else our gov does that is important) that getting reliable facts about them is like asking where the aliens are being held.

Some random video on some site by a channel I never heard of with official sounding voices with gravitas is not going to inform my understanding.

I am presupposing therefore that they are real. Because virtually everything Alex Jones has postulated over the decades has become fact.