What's a gerund? Does it have something to do with Jer's errands? Well, if his legs are tired from all the running, then running is the gerund! Let us further explain.
 
Quite simply, a gerund is a word that has -ing added to a base verb, which is the present participle of a verb. The difference is that gerunds are used as nouns. (Driving is required.)  When the verb in the -ing form is used as a verb or an adjective, it is usually a present participle. (She was fishing for compliments.)
 
Reading, writing, and thinking are things you may do when you see this article. In fact, in that last sentence, we used a gerund phrase as the subject of the sentence.
 
Here are other examples of how gerunds function:
 
1. Object of a preposition: After brushing her teeth, she went to bed.
**Be careful not to dangle the gerund.
Right: After learning the specifics, he could make plans easily. (He learns.)
Wrong: After learning the specifics, plans were easily made. (Plans do not learn.)
 
2. Object of a verb: She loves singing in the shower.
 
3. Subject of a verb: Writing is a difficult task.
 
4. Subject complement with a linking verb: His errors were making him crazy.
 
5. Possessive noun: One of my pet peeves is hearing his singing to the radio.
Wrong: One of my pet peeves is hearing him singing to the radio.
 
6. In a passive sense (used after the verbs want, need, or require):  This house needs cleaning.
 
7. After a preposition—if you use a verb after a preposition, you must use a gerund (no exceptions):  Please sign the memo before leaving.
 
For more information on gerunds, take a look at: http://www.chompchomp.com/terms/gerund.htm and http://en.wikipedia.org/wiki/Gerund.