There are two kinds of dageshim:  more here or this video
| dagesh lene    video | dagesh forte    video | 
| A dagesh lene makes the pronunciation of a BGDKFT letter hard; e.g. a ב is pronounced “v”. A בּ is pronounced “b”. | A dagesh forte doubles the pronunciation of a letter. | 
| Only occurs in BGDKFT letters. | Never occurs in a guttural. | 
| Never preceded by a full vowel. | Always preceded by a full vowel. | 
Note #2: the dagesh in a vav-conversive will never appear in the first letter of the verb root.
