What are some key characteristics that define the 1920s time period so far?

There are many typical characteristic for 20s:  

I WW and some of "reorganization" of the word which caused:

new trends in makeup and fashion - changes when it comes to wearing corsets, or pants (by woman), more independent style, very brave as for that periond of time (e.g. flapper girls); new hairstyles for woman (much more practical), femme-fatale makeupgreat era of silent movies, cabaretsnew trends in music and dance - jazz, swing, etc

We can simply say that after the I WW began a new order not only in political connections but also in people's lifestyle.