Toddlers eat poop either just because of normal toddler behavior and exploration or because of Pica.
Some toddlers who eat poop do so because of Pica which is a disorder that causes the toddler to eat things they shouldn't such as poop, dirt etc.
Although some toddlers eat poop just because they are exploring and are new to the world.
But eventually the toddler will outgrow the eating of his or her own poop although you should still try to curb the behavior and distract the toddler with something else.
If the toddler is not potty trained and wearing diapers then you need to keep them from accessing their diaper and change the poopy diaper as soon as possible so they don't have access to their poop.
It is normal for a toddler to eat their poop.
Just like it's also normal for a toddler to play with their poop but although it's normal for the toddler to eat their poop it needs to be stopped.
If the toddler is in diapers and digging the poop out of their diaper and eating it you need to watch the toddler more closely and change the toddlers poopy diaper before they have a chance to get to the poop.
Or put duct tape on the diaper all the way around it and put the toddler in footie pajamas such as the Little Keeper Sleeper so they have no access to their diaper and poop.
The toddler eating their own poop is unlikely to harm them but it's best to stop the habit as soon as possible because it is gross.
Eventually the toddler will outgrow the phase of eating their poop and playing with their poop though so that is good news.