The term formative assessment is referring to teacher made classroom assessment or common assessments developed by teams of teachers who teach the same core content. Formative assessment also includes interim, benchmark assessments which many school districts purchase from testing companies to measure student mastery of the content 3 or 4 time a school year. Formative assessment's purpose is to guide the instructional process with feedback for both the teacher and learner. Formative should have no accountability consequences.
Summative assessment is normally an end of the year annual assessment. A summative is used for accountability purposes and has some value for feedback to guide the learning process for the next school year.
To summarize, I will use a basketball analogy, think of formative as basketball practice...a time to learn and approve with no high stakes consequences. Think of summative as game night....the score will be kept, results become public and consequences are expected. Hope this helps.
Roger's definition adds to the discussion of Bob's kick-off post on "Four big ideas for Kentucky testing" below. Thanks, Roger!