Oxidizing/Reducing agent

Cu 2+ + 2 e- ----＞Cu (reduction )
Oxidation number decreases from +2 to 0

Fe -------＞Fe 2+ + 2e- (oxidation )
Oxidation number increases from 0 to +2.
The reactant which causes oxidation is oxidizing agent . (Cu 2+ )
The reactant which causes reduction is reducing agent. (Fe )

首先,分左邊隻野 做 oxidation 同reduction 先..
跟住..,,佢隔離果隻就係令佢進行 oxidation /reduction
所以, 係 oxidizing agent /reducing agent.

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i will use english to explain, i hope you can understand^^"

oxidizing agent "always" lose electrons, this process is called reduction.

reducing agent "always" gain electrons, this process is called oxidation.

If you want to distinglish, just count their oxidation number is ok~

Use your example:Fe-->Fe 2+ +2e- Fe 's oxidation number increases from 0 to +2, so Fe is a reducing agent.
Cu 2+ +2e- -->Cu Cu 's oxidation number decreases from +2 to 0, so Cu 2+ is a oxidizing agent.

Give you a summery:
R.A:
1.all metals
2.all halides(GroupVII ions)
3.SO2 , SO3 2-
4.Fe 2+(sometimes change to Fe 3+ but sometimes to Fe)

O.A:
1.all metal ions
2.all halogens
3.NO3-
4.MnO4-, Cr2O7 2-