Whats the difference between feeling depressed, and actually having full out DEPRESSION??

and what are the symptoms??

Depression is much longer lasting that someone who simply is sad/has the blues.

Some symptoms, per mayoclinic.com include the following:
Loss of interest in normal daily activities
Feeling sad or down
Feeling hopeless
Crying spells for no apparent reason
Problems sleeping
Trouble focusing or concentrating
Difficulty making decisions
Unintentional weight gain or loss
Irritability
Restlessness
Being easily annoyed
Feeling fatigued or weak
Feeling worthless
Loss of interest in sex
Thoughts of suicide or suicidal behavior
Unexplained physical problems, such as back pain or headaches

If these things last a week, you're probably just bummed out. If they last for weeks and months on end, then it's most likely depression. Keep in mind one does not have to have EVERY symptom to be depressed. Depression can be treated, particularly if you find a great psychiatrist; trite as it may sound, don't let depression ruin your life....there are many resources out there for you, and many people who want to help you recover from depression.

You might be just depressed from a temporary thing, like you lost a basketball game. Usually the only symptom here is sadness.

Now full out depression has many symptoms. Usually when you are suffering depression you don't eat a lot, your anti-social (not talking to friends/family), you give up your hobbies, your always down (never cheerfull/ always tired), and suicidal thoughts.. It is something that should be seen to a doctor immediately as it can lead to more harmful things.

you get depressed over small things and get over it. Depression that hit hard and never seem to end is like a black hole and you just can't find anything worth getting out of bed for. Nothing helps but a good doctor and time to heal.