some clarifications

Overall-architecture.md

@@ -103,7 +103,7 @@ This protocol proved great robustness in real world testing. Thus whole backend
 
 ### Worker - File Server communication
 
-Worker is communicating with file server only from _execution thread_ (see picture above). Supported protocol is HTTP optionally with SSL encryption (**recommended**, you can get free trusted DV certificate from [Let's Encrypt](https://letsencrypt.org/) authority if you have not one yet). If supported by server and used version of libcurl, HTTP/2 standard is also available. File server should be set up to require basic HTTP authentication and worker is capable to send corresponding credentials with each request.
+Worker is communicating with file server only from _execution thread_. Supported protocol is HTTP optionally with SSL encryption (**recommended**, you can get free trusted DV certificate from [Let's Encrypt](https://letsencrypt.org/) authority if you have not one yet). If supported by server and used version of libcurl, HTTP/2 standard is also available. File server should be set up to require basic HTTP authentication and worker is capable to send corresponding credentials with each request.
 
 #### Worker side
 
@@ -161,7 +161,7 @@ server, its IP address and port is configurable in the API.
 - **eval** -- evaluate a job. Requires at least 4 frames:
     - `job_id` -- identifier of this job (in ASCII representation -- we avoid endianness issues and also support alphabetic ids)
     - `header` -- additional header describing worker capabilities. Format must be `header_name=value`, every header shall be in a separate message frame. There is no maximum limit on number of headers. There may be also no headers at all.
-    - empty frame (with empty string)
+    - empty frame -- frame which contains only empty string and serves only as breakpoint after headers
     - `job_url` -- URI location of archive with job configuration and submitted source code
     - `result_url` -- remote URI where results will be pushed to
 
@@ -204,10 +204,10 @@ Message JSON format is dictionary (associative array) with keys:
     - FAILED -- something bad happened and job was not executed at all
     - UPLOADED -- results are uploaded to fileserver
     - STARTED -- evaluation of tasks started
-    - ENDED -- evaluation of tasks is finished
+    - ENDED -- evaluation of all tasks finished, worker now just have to send results and cleanup after execution
     - ABORTED -- evaluation of job encountered internal error, job will be rescheduled to another worker
-    - FINISHED -- whole execution is finished and worker ready for another job execution
+    - FINISHED -- whole execution finished and worker is ready for another job execution
-    - TASK -- task state changed -- see below
+    - TASK -- task state changed, further information will be provided -- see below
 - **task_id** -- id of currently evaluated task. Present only if **command** is "TASK".
 - **task_state** -- state of task with id **task_id**. Present only if **command** is "TASK". Value is one of "COMPLETED", "FAILED" and "SKIPPED".
     - COMPLETED -- task was successfully executed without any error, subsequent task will be executed