These tools are educationally designed 'quizzes' and forms. They are designed to be a quick and fun way to demonstrate learning.
Most of these tools are limited in the inability to have answers that are 'open' i.e. that all rely on 1 (or more..) correct answers, with no allowance for alternative thinking.
The greatest power in all of these tools is for students, not teachers, to create the content.
These tools all allow learners to;
contribute to learning
demonstrate the recall of their knowledge in a fun way
create content to 'quiz' others - more valuable than simply teacher created.