Summarize the following:
Different temperatures are desirable for different applications. When your sugar reaches the desired temperature for your particular recipe, it is done. Use it immediately.  Thread stage: 223 to 233 °F (106 to 112 °C) A teaspoonful of sugar will form thin threads when dipped into and removed from cold water. It is good for candying fruits and nuts.  Soft-ball stage: 235 to 240 °F (113 to 116 °C) A teaspoonful of sugar will ball when dipped in cold water; the ball immediately flattens when removed from the water. It is good for making fudges and fondants. Firm-ball stage: 245 to 248 °F (118 to 120 °C) A teaspoonful of sugar will ball when dipped in cold water; the ball holds its shape when removed from the water but loses it when it reaches room temperature or pressed. It is good for making caramel candies. Hard-ball stage: 250 to 266 °F (121 to 130 °C) A teaspoonful of sugar will ball when dipped in cold water; the ball squish slightly when pressed or will be hard and sticky when removed from the water. It is good for making divinity or marshmallows. Soft-crack stage: 270 to 290 °F (132 to 143 °C) A teaspoonful of sugar will separate into pliable threads when dipped in cold water. Hard-crack stage: 295 to 310 °F (146 to 154 °C) A teaspoonful of sugar will separate into brittle threads when dipped in cold water. Caramel stage: 320 to 350 °F (160 to 177 °C) The sugar will brown in the pan and start to have a caramel smell.

Summary:
Look for the appropriate doneness.