contains Search the filter keyword in the field content example: Search 'erp' in 'openerp'

not contains Search the string not contains the keyword example: 'openerp' non contain 'sap'

equals Search the some string example: 'erp' equals 'erp' or 'ERP' or 'Erp'

is not equal Search the string not equals to keywork example 'OpenERP' not equals 'SAP'

is set Search the records when the field has a value (it's not important the value itself, it's important it exists)

is not set Search the records without a value

less than, greater than Search the records where the field has a value lesser (or greater) then your keyword value

less than or equal, greater than or equal Like the other but search the record with a value equal to keyword, too

an extra point to note with advanced search filters. if you have multiple conditions in the same advanced filter they are OR statements. if you need AND statements, do multiple advanced filters within the same view