What does 420-Friendly mean?

If somewhere is 420-friendly then this means that they are happy for you to smoke cannabis on their premises. This is now common in many US states, as well as places in Europe, particularly in the Netherlands.

Why is 420 so important for weed smokers?

4.20 pm on April 20 is a special day for weed smokers as it celebrates an important part of their lifestyle. As mentioned above, the term can be dated back to 1971, originating in California when 5 high school students set out to locate an abandoned cannabis crop.