Use Append in this sample code?

The first Append doesn’t work, but the second does. The difference is the semicolon. I don’t understand this.The problem doesn’t depend on Append. The same phenomenon occurs with Union or Insert. I overlook something.

points = {{0, 0, 0}, {1, 1, 0}, {0, 1, 1}, {1, 0, 1}};

In[266]:= pointsums = {}

Out[266]= {}

In[267]:= Append[pointsums, points[[2]]];

In[268]:= pointsums

Out[268]= {}

In[269]:= Append[pointsums, points[[2]]]
pointsums

Out[269]= {{1, 1, 0}}

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int = Integrate[1/(x^3 - 1), x];
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It seems that you expect from Append the behaviour of AppendTo. Take a minute to look them up.

forget it, I see it

forget it, I see it

forget it, I see it