What is the difference between yield point and elastic limit?

Elastic Limit as you correctly defined is the point at which a further increase in stress leads to permanent deformation, it is shortly after the limit of proportionality, so the material might not obey Hooke's law but the deformation would be still elastic.

Yield point is the point at which a further increase in stress leads to a much larger increase in extension/stress, and is the reason you have that curved down part before the material breaks, it is after the elastic limit.

If you have done a Hooke's law experiment in class you will notice that if you put enough masses eventually the spring hugely stretches just by adding 1 more mass, that's the yield point hit.