Updated Usage (markdown)

Usage.md

@@ -123,7 +123,7 @@ global plugin arguments:
 
 ```
 
-## Targets
+## Targets / Target Files
 
 Targets are the only required argument for AutoRecon to function. Targets are accepted in various formats (single IP addresses, CIDR notation for ranges, and even hostnames that are resolvable by the OS.
 
@@ -145,4 +145,34 @@ The file can be passed to AutoRecon in either of the following ways:
 ```
 autorecon -t /path/to/file
 autorecon --target-file /path/to/file
+```
+
+## Ports
+
+By default, AutoRecon scans ports according to the selected PortScan plugins, which are a top 1000 TCP port scan, an all (65,535) TCP port scan, and a top 100 UDP port scan (if AutoRecon is running with sufficient permissions). With the `-p` or `--ports` command line option, AutoRecon will only scan a subset of ports.
+
+All PortScan plugins have access to the list of ports requested (which is empty if the user does not specify them), and it is ultimately up to the plugin author to decide whether or not the plugin should (a) scan the default ports, (b) scan the ports specified, or (c) not scan any ports at all. Option (a) should rarely be considered, while options (b) and (c) are recommended. For example, the top 1000 TCP port scan plugin checks to see if ports were specified by the user, and if they were, doesn't perform any scanning. Instead, the all TCP port scan and top 100 UDP port scan plugins will scan the specified ports.
+
+Ports can be specified in a number of ways, both as single ports, and as port ranges, separated by commas. The following example will scan both TCP and UDP port 80 and 443:
+
+```
+autorecon -p 80,443 <target>
+```
+
+The following example will scan TCP and UDP ports 20 to 23 inclusive:
+
+```
+autorecon --ports 20-23 <target>
+```
+
+To scan specific TCP (or UDP) ports, preface the port(s) with either a `T:` for TCP, or `U:` for UDP. The following example will scan TCP ports 20 to 23 inclusive, as well as UDP ports 53 and 123:
+
+```
+autorecon -p T:20-23,U:53,123 <target>
+```
+
+To scan the same TCP and UDP port, but also scan specific TCP and/or UDP ports, put the shared ports at the start, or preface them with a `B:` for Both. The following example will scan TCP and UDP ports 53 and 88, as well as TCP ports 80 and 443, and UDP port 123:
+
+```
+autorecon --ports 53,T:80,443,U:123,B:88
 ```