difference between improve and enhance

enhance - (нэмж сайжруулах) Enhance means to make sth look better by increasing its value or beauty.
improve - (сайжруулах)Improve means to become or make sth better

what's the difference between 'improve' and 'enhance'?

(is 'improve' used in real life more than 'enhance'? I guess 'enhance' has more formal meaning. is that right? thanks to put up with my mumble jumble.)

• Improve means to become or make sth better but Enhance means to make sth look better by increasing its value or beauty.

• "Improve" means to increase the level of quality.
  
  "Enhance" means to take one element and lift it to a greater degree (the old meaning was simply "to make higher").
  
  You can see there may be some overlap, however "improve" can only be used in positive situations. To illustrate:
  
  "My bad mood was improved by her actions." = you felt better.
  "My bad mood was enhanced by her actions." = you felt worse.

• There is very little difference between improve and enhance. One could argue that the difference is in the amount of change that is made. An enhancement is likely to be a small change or addition to an item. An improvement could be anything from a small change to a complete redesign of an object.
  
  The enhancements made to the vacuum improved its sales.
  The improvements made to the vacuum enhanced its sales.

• To enhance is to add something.
  
  To improve is to make the something better - no additions, just improvement of what was already there.

• In some instances, enhance and improve could be used interchangably but there might be subtle or even major differences in meaning.
  
  Adding a bit of dill weed to the spaghetti sauce enhances its flavor.
  --> Something has been added which makes the flavor of the sauce better or might heighten or blend the flavors already there so it tastes even better. 
  
  Adding a bit of dill weed to the spaghetti sauce improves its flavor.
  --> The flavor is better by adding the dill weed. The implication is that the flavor was not so good before. It may still not be good, but it is better than it was before. In the previous sentence, there is no such implication that the flavor wasn't good before adding the dill weed.
  
  Your violin performances will improve only if you practice more.
  --> The performances are likely not very good, and they need to get better. This will happen only if the performer practices more.
  
  Your violin performances will be enhanced only if you practice more.
  --> This sentence doesn't make sense except in the case in which surrounding context would tell me that the performer needs to practice playing before people more. His/her skill is good but shyness or stage fright is preventing him/her from playing to the height of his/her ability.
  
  Your violin performances would be enhanced if you play in the other corner.
  --> The violinist is playing very well, but the location he/she is performing in is detracting from the quality of the performance. By changing the location he/she is playing in the audience's perception of the performance would get better because they could hear it better.