What does the negative sign in the expression $E_{Zn^{2+}|Zn}^o = -0.76 \ V$ mean?

Fluorine is the best oxidising agent because it has

Standard potential of electrode reaction $Cu^{2+}_{(aq)} + 2e^{-} \rightarrow Cu_{(s)}$ is $+0.34 \ V$. What is the standard potential of the reaction $2Cu_{(s)} \rightarrow 2Cu^{2+}_{(aq)} + 4e^{-}$?

When a rod of metal $A$ is dipped in an aqueous solution of metal $B$ (concentration of $B^{2+}$ ion being $1 \ M$) at $25 \ ^oC$,the standard electrode potentials are $E^o_{A^{2+}/A} = -0.76 \ V$ and $E^o_{B^{2+}/B} = +0.34 \ V$. What will happen?

Calculate the standard cell potential $(E_{cell}^{o})$ for the following electrochemical cells:
$(i)$ $Al_{(s)}|Al_{(1M)}^{3+}||Cu_{(1M)}^{2+}|Cu_{(s)}$
$(ii)$ $Al_{(s)}|Al_{(1M)}^{3+}||Zn_{(1M)}^{2+}|Zn_{(s)}$
$(iii)$ $Al_{(s)}|Al_{(1M)}^{3+}||Ag_{(1M)}^{+}|Ag_{(s)}$
$($ Given: $E_{Al^{3+}|Al}^{o} = -1.66 \ V$,$E_{Zn^{2+}|Zn}^{o} = -0.76 \ V$,$E_{Cu^{2+}|Cu}^{o} = 0.34 \ V$,$E_{Ag^{+}|Ag}^{o} = 0.80 \ V$ $)$

Hydrogen gas is not liberated when the following metal is added to dil $HCl$.