Create Column

Sure, SEARCH and all other DAX functions are defined here:

https://docs.microsoft.com/en-us/dax/search-function-dax

Also, intellisense will tell you what is what when typing DAX formulas. But in SEARCH's case, first see my second post because you don't need the -1 I believe, but SEARCH has the format:

SEARCH( <search text>, <within text>, <start position>, <alternate return value if not found> )

So, let's tackle the second part, the SWITCH(TRUE()...) construct allows you to have any DAX that returns a logical value on the left side, so you read the SWITCH like:

SWITCH(

  TRUE(),

  <logical condition 1>, <return value 1 if logical condition 1 is true>,

  <logical condition 2>, <return value 2 if logical condition 2 is true>,

  ... (as many of these as you want)

  <default return value optional>

)

Now, logical conditions can include && and || for AND and OR so:

SWITCH(TRUE(),

  SEARCH("AIX 5.1") || SEARCH("AIX 6.3") || SEARCH("AIX 99.83"),"AIX",

for example. Or any combination of logic. You can use parens like:

( this || that) && this other thing

for example.