Correct

的确 vs 确实

/ díquè vs quèshí /
Strokes

Definition

的确 is an Adverb, 确实 is an Adjective, both words mean [certainly; real; certain]. 

Example

的确 and 确实 both mean "absolutely true". But 的确 is an Adverb and can only be an Adverbial. 确实 can be used as quite a few sentence elements. Both words can be reduplicated. As an adverbial, they are interchangeable.
1
què
的确
  
(
quèshí
确实
  
)
shuō
guò
zhè
gōu
huà
  

It's true that he said it.

2
de
quèquè
的确确
  
(
quèquèshíshí
确确实实
  
)
shì
zhōngxué
中学
tóngxué
同学
  

It's true that she and I are middle school classmates.

When 确实 functions as other sentence elements, 的确 cannot replace it.
3
Zhè
xiāoxi
消息
quèshí
确实
  

The news is unreliable. (predicate)

4
Qǐng
gào
告诉
chū
出发
quèshí
确实
日期
  

Please tell me the exact start date. (attributive)

5
Zhèxiē
这些
shù
数字
yào
gǎo
de
quèquèshíshí
确确实实
de
  

The figures should be precise. (complement)