In plain English
SOPR looks at coins that actually moved today. If they sold above what they last moved at, SOPR is above 1 (profit-taking). If they sold below, SOPR is under 1 (loss-taking).
Dips under ~0.95 mean coins are moving at a real discount to cost — often late-bear capitulation. Stretches above ~1.08 are euphoric profit-taking. The 1.0 line is break-even spent coins.