Adding platform details to README

Added state descriptions for Grill State, Heating State and. Probe State sensors.

README.md

@@ -30,6 +30,45 @@ Platform | Description
 6. Restart Home Assistant
 7. In the HA UI go to "Configuration" -> "Integrations" click "+" and search for "Traeger"
 
+## Platform Details
+Some of the platforms are fairly self explanatory, others could use a little more explaining. Below are more details on some of those platforms.
+### Grill State Sensor
+This sensor aligns with the status values in the Traeger app.
+State | Description
+-- | --
+`offline` | Powered off (or not accesible)
+`sleeping` | Standing by (power switch on, screen off)
+`idle` | Standing by (power switch on, screen on)
+`igniting` | Igniting the fire pot
+`preheating` | Ignition is complete, heating to set temperature
+`manual_cook` | Cooking mode
+`custom_cook` | Cooking mode, using preset cook cycle
+`cool_down` | Cool down cycle
+`shutdown` | Cool down cycle complete, heading to sleep
+`unknown` | Unkown state, report to developers
+
+### Heating State Sensor
+This sensor tries to provide more useful insight into the heating status of the grill. Many of these values can be trigger off of to provide notifications that are not available in the Traeger app.
+State | Description
+-- | --
+`idle` | Not in igniting, preheating, cooking or cool_down modes
+`preheating` | Igniting or preheating (and under 165°F)
+`heating` | Trying to get temperature **up** to new target temperature
+`cooling` | Trying to get temperature **down** to new target temperature
+`at_temp` | Temperature has reached the target temperature (and is holding at ±20°F of target temperature)
+`over_temp` | Was `at_temp`, but is now more than 20°F **above** target temperature
+`under_temp` | Was `at_temp`, but is now more than 20°F **below** target temperature
+`cool_down` | Cool down cycle
+
+### Probe State Sensor
+This sensor provides triggers for useful probe events such as being close to the target temperature or reaching the target temperature.
+State | Description
+-- | --
+`idle` | Probe target temperature is **not** set
+`set` | Probe target temperature **is** set
+`close` | Probe temperature is within 5°F of target temperature
+`at_temp` | Probe alarm has fired
+`fell_out` | Probe probably fell out of the meat (Probe temperature is greater that 215°F)
 
 ## Installation (HACS)