Assessment is a tool/process by which we assign value to someone's/something's performance or knowledge or skills or prowess or wealth, based on some chosen measurement (often chosen by someone else). I know, there sure are a lot of "somes" in that sentence. Adds to the clarity, huh?
Summative assessments are snapshots taken of that someone/something on a rather infrequent time frame, often annually. For students, we have become accustomed to testing them once per year with a really long test, presumably to find out whether they have learned what they were supposed to over that year of time. For us big people, it might be a measurement of our net worth on March 1 of each year or our body weight on each January 1 (ouch!). A summative assessment is a little like an autopsy, an after-the-fact, backward-looking evaluation.
Formative assessments are ongoing evaluations, taken hourly, daily, weekly, or monthly. Formative assessments are more like a movie-in-progress (as opposed to a snapshot). Formative assessments can be likened to frequent, regular monitoring of personal health markers (like weight, blood pressure, cholesterol levels, pulse rates, etc.). They measure current progress, with an eye on what growth/development/learning needs to happen next - the next minute, the next hour, the next day, the next month. Generally, formative assessment is viewed in the context of cumulative progress to date.
Summative assessment is most often used to compare or sort or rank someone/something with some other someones/somethings. Formative assessments are most useful when we're trying to get some sense of authentic and current growth/performance, as individuals or organizations - it's our progress being measured against our own previous progress or performance.
How, then, shall we choose to measure our lives? Formative for me please.