What is the meaning of LIKE or _% used in SELECT statements?

Like is used to search for patterns in a string, such as column name like 'pattern character'.

_ is any single character and % is any string of "0 or more characters", so 'like'_vegetable%' searches for one character before 'vegetable', and 'vegetable' after 'vegetable'.

create table test1(
  comment varchar(255)
);
insert into test1 values('I love vegetables');
insert into test1 values('I love hot vegetables');
insert into test 1 values ('hot vegetables');
insert into test 1 values ('I love pesticide-free vegetables');

select * from test1 where comment like '_vegetable %';

Run Results

I love hot vegetables
hot vegetable

• "I love vegetables" is not selected because there is no letter in front of "vegetables."
• "I love pesticide-free vegetables" is not selected because the front of "vegetables" is three letters long.

http://sqlfiddle.com/#!9/184e0/1

_ and % are wildcards.

Since _ represents any single character, LIKE "_vegetables" includes
vegetables, raw vegetables, etc. % represents any string of at least 0 characters, and LIKE "vegetable %" is affected by such things as "vegetable" or "vegetable juice."

https://technet.microsoft.com/ja-jp/library/ms187489(v=sql.105).aspx

Is there a use case?

SELECT* FROM tblName WHERE fieldName LIKE'_Vegetable %'

SELECT [Field you want to display] 
FROM [Table Name] 
WHERE [Field to be searched] LIKE '[Search Pattern]'

[Search Patterns] can use wildcards.
The wildcard is described by someone else, so please refer to it for more information.