Bulls want to jump in on the hype (along with the herd) hoping that some other bulls jump in right after they do so that they make money. They expect to buy and hold because the company is seen to be in good shape.
Bears, on the other hand, look for areas where supply overwhelms demand. They want to short sell to these bulls. In other words, borrow from a broker to sell to those who want to buy. Then buy at a lower price to return to the broker.
Usually, there is good news just as price reaches an area where institutional supply overwhelms demand. Therefore, the bears wait on the run to pounce.
Here we see MKS .L rising quite well over the past few weeks. Business must be good. The FTSE100 is beginning a rally back to 7000 and so everything is rosy. Marks and Spencer also happen to have broken their 14 quarter run of declining this quarter. This is fantastic news.
Investors buy stock based on this "news". Excessive demand causes prices to open 4% higher on April 2 (Late April Fools' prank). This rally, which presumably profited some in the short-term, drove straight into an area where willing sellers were in their numbers. We know this because price fell dramatically from here the last time (in 2008).
If there is still plentiful supply, price should now fall to at least 530.00. Entry was missed at 555.70 on this one but hopefully there is a retest of that area before prices fall. Orders were placed on the M5 chart to allow risk of 2-3 base points.