The arrows are not terribly obvious, but once you know about them, you'll start to notice them. Let me illustrate.
Here is a portion of Family Tree.
You probably already know about the arrow to extend the pedigree and maybe even the one to show the list of children. But, what about the one beside the name of the husband and another beside the name of the wife and the one to the left of the couple box? And do you notice that not all couples show these arrows? So, click them (it pays to have a healthy case of curiosity when doing family history)!
ESPECIALLY click the arrows you see to the left of a couple box. That one means that Family Tree shows more than one set of parents for the person to the left of that couple box. And, since most of us only get one set of parents, that is often a problem. Most often it occurs because there are duplicate sets of parents, as below.
It looks like Johann Georg Brandter is also in as Brenner. Ann Margaretha is probably linked to both as a spouse. I won't go into the details of fixing this in this post. But, basically, you need to click Anna Margaretha Sachs' record. Look at her spouses. Do some research to discover the correct name for her husband. Merge if you determine they are duplicates. In other words, take the time and effort to clean up the record.
How about those arrows beside each name in the couple box? Those mean that each shows with more than one spouse.
Anna shows with the 2 spouses we saw in the couple box arrow list. Which tells me she is not a duplicate (one less record to need to merge). To fix this one, you need to do some research. Who was her husband? What was his correct name? Merge if duplicates; remove relationships if one is simply the wrong fellow.
Johann shows 3 wives: one is unknown. That one you can get rid of just by removing any children that show in that relationship (after you make sure they show with the correct set of parents). For the other two, some research is needed to figure out who his wife was and remove the relationship to the one that is not his wife (or merge if they are duplicates).
Bottom line--don't just ignore those arrows. Often users of Family Tree do ignore the arrows if the pedigree shows the relationships they believe are correct. This can be because they just don't want to (or don't feel they know how) do the research to clean it up, or don't have a clue how to fix incorrect relationships. But, you'll be sorry if you don't fix them--others will add stuff to some of those relationships and the tree will just get messier and messier until you feel like tearing out all your hair and giving up altogether.
If you need help fixing incorrect relationships or fixing other things you see that are wrong, check out my Table of Contents for posts that might be helpful. And, if you have a specific mess and want specific help, feel free to comment on this (or any other) post and I'll get you the info you need. With your permission, I'll answer in the blog so others can learn along with you.