This was an appropriate movie for the 1970s where long hair, drugs, wild clothing, war protests and just all-around rebellion was the "in" thing to do, although rebellion has been a part of society since Adam and Eve.
In this film, we have the famous Hippie "brothers" of the era: Cheech Marin and Tommy Chong ("Cheech and Chong," as they were known back then) with a story strictly about getting stoned (as we called it then.)
Actually, there are some very funny scenes in here, such as these two clowns smoking the huge, huge joint while driving down the road. Then, we see the car almost white with smoke and the two guys so stoned they don't realize they are parked. That, and a couple of other scenes were funny but overall it's predictable in the negative aspects: language (Strother Martin) , gratuitous sex and and the general irreverence of the 1960s and '70s "counterculture."
And...oh, yeah, the two boys finish every sentence with the word "man." Well, all I can say is the film had it's day, man, but is a bit dated by now, man! (But still funny!)