I think you mean that you want each record to have a list of keywords (tags) specific to that record and then, when you select multiple keywords in a global field, you can pull up a list of records that match any one of the selected keywords.
Is that it?
If so, you can build your list of tags for each record in one of two ways:
1) Use a text field and enter each keyword into this text field separated by returns. If you then load a global field with keywords (can be done with any number of methods, including a real or apparent list of check boxes), this relationship:
Table 1::globalList = Table 2::RecordList
Can be used to display a list of records from Table 2 in a portal or Go To Related Records can pull up a found set of Table 2 records in a list or table view.
2) Use a Join table to link a table of keywords to your table of individual records. Use the same Global Field and relationship set up, but define the relationship to link to the join table instead of Table 2. This is nearly the same method, but it is often easier to manage your list of tags for each record using a join table instead of a single field listing multiple values.
If you have FileMaker Advanced, you may want to examine the KeywordParse custom function in the Known Bugs List database to see one way for generating a list of tags from multiple text fields.