diff --git a/docs/API.md b/docs/API.md
index 3bd09c51..019f0c32 100644
--- a/docs/API.md
+++ b/docs/API.md
@@ -51,8 +51,8 @@ is serving, in between `mg_poll_server()` calls.
     void mg_poll_server(struct mg_server *server, int milliseconds);
 
 This function performs one iteration of IO loop by iterating over all
-active connections, performing `select()` syscall on all sockets, and sleeping
-for `milliseconds` number of milliseconds. When `select()` returns, Mongoose
+active connections, performing `select()` syscall on all sockets with a timeout
+of `milliseconds` number of milliseconds. When `select()` returns, Mongoose
 does an IO for each socket that has data to be sent or received. Application
 code must call `mg_poll_server()` in a loop. It is an error to have more then
 one thread calling `mg_poll_server()`, `mg_set_option()` or any other function
diff --git a/docs/Internals.md b/docs/Internals.md
index 891686dc..ee99f7b3 100644
--- a/docs/Internals.md
+++ b/docs/Internals.md
@@ -1,21 +1,42 @@
 # Mongoose Internals
 
 Mongoose has single-threaded, event-driven, asynchronous, non-blocking core.
-When mongoose server instance is created, it contains an information about
-the configuration and the state of each connection:
+`mg_create_server()` creates a web server instance. An instance is a container
+for the config options and list of active connections. To do the actual
+serving, user must call `mg_poll_server()`, which iterates over all
+active connections, performing `select()` syscall on all sockets with a
+timeout of specified number of milliseconds. When `select()` returns, Mongoose
+does an IO for each socket that has data to be sent or received. Application
+code must call `mg_poll_server()` in a loop.
 
-    struct mg_server {
-      sock_t listening_sock;          // Listening socket
-      union socket_address lsa;       // Listening socket address
-      struct linked_list_link active_connections;
-      struct linked_list_link uri_handlers;
-      char *config_options[NUM_OPTIONS];
-      ...
-    };
+Mongoose server instance is designed to be used by a single thread.
+It is an error to have more then
+one thread calling `mg_poll_server()`, `mg_set_option()` or any other function
+that take `struct mg_server *` parameter. Mongoose does not
+mutex-protect `struct mg_server *`, therefore the best practice is
+to call server management functions from the same thread (an IO thread).
 
-A server instance is capable on listening on only one port. After creation,
-a server instance has a list
-of active connections, initially empty. It has a list of URI handlers,
-initially empty, and configuration parameters. Configuration can be
-altered by `mg_set_option()`, and new URI handlers could be added by
-`mg_add_uri_handler()`.
+
+It is an error to pass and store `struct mg_connection *` pointers for
+later use to send data. The reason is that they can be invalidated by the
+next `mg_poll_server()` call. For such a task,
+there is `mg_iterate_over_connections()` API
+exists, which sends a callback function to the IO thread, then IO thread
+calls specified function for all active connection.
+
+When mongoose buffers in HTTP request and successfully parses it, it calls
+appropriate URI handler immediately for GET requests. For POST requests,
+Mongoose delays the call until the whole POST request is buffered in memory.
+POST data is available to the callback as `struct mg_connection::content`,
+and POST data length is in `struct mg_connection::content_len`.
+
+Note that websocket connections are treated the same way. Mongoose buffers
+websocket frame in memory, and calls URI handler when frame is fully
+buffered. Frame data is available `struct mg_connection::content`, and
+data length is in `struct mg_connection::content_len`, i.e. very similar to
+the POST request. `struct mg_connection::is_websocket` flag indicates
+whether the request is websocket or not. Also, for websocket requests,
+there is `struct mg_connection::wsbits` field which contains first byte
+of the websocket frame which URI handler can examine. Note that to
+reply to the websocket client, `mg_websocket_write()` should be used.
+To reply to the plain HTTP client, `mg_write()` should be used.