the lagging strand
At the same fork where one new strand is built smoothly, the other new strand has an awkward problem: it needs to grow in the opposite direction from the way the fork is opening. Since DNA polymerase can only build 5'-to-3', it cannot simply follow the fork on this strand. Instead it has to wait for some template to be exposed, then dash backward toward the fork in a short burst, again and again. This stop-and-start strand is the lagging strand.
Here is the trick in plain steps. As helicase opens more template, primase lays down a new RNA primer near the fork. The polymerase then extends that primer 5'-to-3' away from the fork (back toward the previously copied region) until it bumps into the last fragment, making one short piece called an Okazaki fragment. Then the fork opens more, a new primer is laid, and another fragment is made. The result is a series of short fragments built backwards relative to fork movement; each one still grows 5'-to-3', honouring the polymerase's only rule.
Finishing the lagging strand is extra work: the RNA primers must be removed and replaced with DNA, and DNA ligase must seal every gap between fragments into one continuous strand. The lagging strand is the price the cell pays for the antiparallel structure of DNA combined with a polymerase that goes only one way. It is why replication, though astonishingly fast, needs primase firing repeatedly, many short fragments, and a ligase to stitch them up.
Think of sewing forward while walking backward: you can only stitch toward yourself, so you take a step back, stitch a short run toward your last stitch, step back again, and repeat. Each backstitch is an Okazaki fragment, and the whole seam must later be tied off (ligated) into one thread.
Built backwards in short pieces, then stitched together.
Even on the lagging strand, every fragment is still made 5'-to-3' — the strand only appears to grow 'backward' relative to the fork because it is assembled from discontinuous pieces, not because the polymerase ever runs the other way.