Role of Airnode update (#666)

* Role of Airnode update
Changed this up to be as simple as possible. This is probably hte most important section in teh dAPI reference section in my opinion so let's keep on perfecting it.

* beacon value double talk

docs/reference/dapis/understand/index.md

@@ -55,15 +55,14 @@ noticeably is its implementation of the request-response protocol (RRP) and data
 feeds.
 
 An Airnode is owned by an API provider and is used to call API provider
-endpoints to fetch and sign data. Airnode interfaces with these operations and
-gathers its signed data at the request of Airseeker. Airseeker uses the signed
-data to determine if the deviation of a dAPI value (e.g., plus or minus 0.25%,
-0.5%, 1%) warrants an on-chain update of its beacon(s).
+endpoints to fetch and sign data at the request of Airseeker. Airseeker uses the
+signed data to determine if the deviation of a beacon value warrants an on-chain
+update.
 
 <img src="../assets/images/beacons-airnode.png">
 
-In the diagram above, companies XYZ and ABC both provide ZIL/USD values, A and
-B, respectively, that are aggregated to determine the dAPI ZIL/USD value.
+In the diagram above, companies XYZ and ABC both provide ZIL/USD beacon values,
+A and B, respectively, that are aggregated to determine the dAPI ZIL/USD value.
 Airseeker regularly checks the deviation of ZIL/USD using the sign data from
 these Airnodes. Airseeker will update the corresponding beacons behind ZIL/USD
 when deviation is detected.