Let's review each of the concepts to understand and differ them better.
Trend Line
Recall that a trend line is a line that approximates the relationship between the variables or data sets of a scatter plot. There is no unique trend line. We trace them according to what we think follows the behavior of our data well, or by using two data points.
All of the lines shown above are examples of trend lines. Notice that some of them fit better in certain regions, but worse in others.
Line of Best Fit
A line of best fit is a special case of trend line. This is the most accurate of the trend lines when describing the whole data set, because it uses all the data points. We only have one line of best fit for a given data set.
Conclusions
We can summarize the differences between both types of lines using a table.
Trend Line
Line of Best Fit
Are traced by hand following the data behavior or using two data points.
It is calculated using all the data points.
There can be many of them.
It is unique for a given data set.
They model the data considerably well. Some of them are better at certain regions of the data set than others.
It models the global behavior of the data set better than any other trend line.
