This is quite simple where we want to get Get a single record by passing Primary key of the record which means we have Primary field value that is GUID ( Case has Account lookup )
i.e Get Account Record where account = <GUID>

This action returns a collection of record for whichever entity is selected, it would be quite easy to understand if we know how to use ODATA query especially Functional or nontechnical,

Click here check how to create a query using ODATA (Its Quit easy)

So, in short, we can apply Almost all Queries of  OData example

1. Filter ($filter) in list Records action to fetch filtered record collection
   i.e data/v9.1/accounts?$filter=statecode eq 0
2. Order By ($orderby) in list Records action to fetch records in Particular Order
   i.e data/v9.1/accounts?$orderby=name desc
3. Top ($top) Count in list Records action to fetch $top Qualifier
   i.e data/v9.1/accounts?$top=5
4. Expand ($Expand) in list records action to pull Related Entity and apply $select to specify Attribute of the related entity
   i.e data/v9.1/accounts?$top=5$expand=primarycontactid($select=fullname)

OData defines a set of logical operators that evaluate to true or false based on which filters are applied

Equals

Not Equals

Greater Than

Greater Than or Equal

Less Than

Less Than or Equal

And

Or

Not

has

Example: all products with a Name equal to ‘Milk’

$filter=Name eq 'Milk'

Example: all products with a Name not equal to ‘Milk’

$filter=Name ne 'Milk'

Example: all products with a Name greater than ‘Milk’:

$filter=Name gt 'Milk'

Example: all products with a price greater than or equal to 100:

$filter=Price ge 100

Example: all products with a price  less than 100:

$filter=price lt 100

Example: all products with a Price less than or equal to 100:

$filter=Price le 100

Example: all products with the Name ‘Milk’ that also have a Price less than 2.55:

$filter=Name eq 'Milk' and Price lt 2.55

Example: all products that either have the Name ‘Milk’ or have a Price less than 2.55:

$filter=Name eq 'Milk' or Price lt 2.55

Example: all products that do not have a Name that ends with ‘ilk’:

$filter=not endswith(Name,'ilk')

Example: all products whose style value includes Yellow:

$filter=style has Sales.Pattern'Yellow'

If a parameter of a canonical function is null, the function returns null.

contains

endswith

startswith

length

indexof

substring

tolower

toupper

trim

concat

year

month

day

hour

Example: all Account with a Name contains ‘DVMSKE’

$filter=contains(name,'dvmske')

Example: all account with a name endswith ‘pvt ltd’

$filter=endswith(Name,'pvt ltd')

Example: all Account with a Name startswith ‘Dubai’

$filter=startswith(Name,'dubai')

Example: all Account with a Name  19 characters Length

$filter=length(Name) eq 19

Example: all Account with a Name containing ‘Dubai’ starting at the second character Index

$filter=indexof(Name,'Dubai') eq 1

Example: all Account with a Name that equals ‘manish chouhan’ once any uppercase characters have been converted to lowercase tolower

$filter=tolower(name) eq 'manish chouhan'

Example: all Account with a Name that equals ‘MANISH CHOUHAN’ once any lowercase characters have been converted to uppercase toupper

$filter=toupper(CompanyName) eq 'MANISH CHOUHAN'

Example: all employees birth year is 1971

$filter=year(BirthDate) eq 1971