You can use filters to show only the lines that include a specific term or string. The filter box is at the bottom of the Phenote window.
The filter interface lets you choose a field to filter on, or you can use the "simple filter" to look for a term (or a string of letters, such as "ab") in any field. Choose the desired filtering field from the pulldown list, or leave it at "Simple Filter".
The fields that are constrained by ontologies offer you a choice of "Exact" (find lines where the field exactly matches the term you've specified) or "Inherit" (include lines where the field term inherits from the term you've specified). The unconstrained fields (including "Simple Filter", which looks at all fields) offer a choice of Exact or Partial match.
Here is an example showing the use of a simple filter and a field-specific
filter. First, here's our sample dataset, unfiltered:

Now the user has applied a Simple Filter to look for all lines that include the
term "Abnormal". Notice that in two lines, this term appears in the Quality
field, and in one, it's in the Abnormal field.

The user has decided she only wants to see terms with Quality=Abnormal, so she
has chosen the Quality field from the filter pulldown. Notice that the line
that had Abnormal in a field other than Quality has disappeared from the
table.

Filters don't permanently remove data from your dataset--they just suppress it temporarily from the display. To see all of your data again, all you have to do to remove the current filter is to delete the text you typed in the filter box.
Also keep in mind that filters are "live"--if you edit your data while a filter is turned on, the newly edited data will be subjected to the filter. So, for example, if you edited the Quality field in the example above and changed "Abnormal" to "Normal", that whole line of data would disappear from the annotation table because it no longer matched the filter. (This can be confusing the first time it happens--where'd my data go?!)