2s10s condenses the whole curve into one number that fits in a headline. Positive and widening means a normal-yield-curve and usually an economy with room to run. Negative means an inverted-yield-curve, which has preceded most US recessions.
Traders watch not just the level but the direction and the driver. Re-steepening from deep inversion, driven by the 2-year falling, has historically arrived close to the start of a downturn rather than safely before it.
Example: the 10-year is at 4.18% and the 2-year at 4.61%. 2s10s is -43 bp. Three months later the 2-year has fallen to 3.95% while the 10-year sits at 4.10%, so 2s10s is +15 bp, a 58 bp bull-steepener.
Related: three-month-ten-year, curve-steepener, curve-flattener, inverted-yield-curve, yield-curve