Integers (Infinite Precision), Reals (Infinite Precision, Machine Precision, Arbitrary Precision), Complexes ((Infinite Precision, Machine Precision, Arbitrary Precision) with some overlap. That’s why the square root of 2 returns the square root of two, to maintain the precision.
In[1]:= Element[1, Integers]
Out[1]= True
In[2]:= Precision[1]
Out[2]= \[Infinity]
In[3]:= Element[2/3, Reals]
Out[3]= True
In[4]:= Precision[2/3]
Out[4]= \[Infinity]
In[11]:= Sqrt[2]
Out[11]= Sqrt[2]
In[10]:= Precision[Sqrt[2]]
Out[10]= \[Infinity]
In[6]:= Precision[1.0]
Out[6]= MachinePrecision
In[7]:= Precision[N[1, 25]]
Out[7]= 25.
In[9]:= Element[2, Complexes]
Out[9]= True
In[8]:= Element[2 + 3 I, Complexes]
Out[8]= True
In[12]:= Precision[2 + 3 I]
Out[12]= \[Infinity]
In[13]:= Precision[N[2 + 3 I, 25]]
Out[13]= 25.