You should look into getting a tool like RegexBuddy. It will explain everything in a given regex, as well as how it compiles and how it branches.
Assuming PCRE or similar:
/ //begin
^ //start of string
\/ //literal /
node? //I assume node is optional, normally it'd be (node)?
//? makes the previous expression optional
(
?: //non-capturing group (think of it like dont capture <this>)
\/ //literal /
(\d+) // one or more digits, 0-9
(
?: // another non-capturing group
\.\. // literal ..
(\d+) // one or more digits 0-9
)
? // optional once more
)
? // make the previous group optional
/ // end