Aww, no nicknames?
Preface: this is mostly background technical stuff that you might want to ignore. If so, just think of characteristics and nature as just flavour.
Every pokemon has six stats: HP, Attack, Defense, Special Attack, Special Defense and Speed.
Moves fall under 3 categories: Physical, Special or Status. Status just means it does something other than damage. Physical vs. Special determines whether Atk/Def or SpA/SpDef are used to calculate damage.
Pokemon natures raise one stat by 10% and lower another stat by 10%. Every combination is present, except no natures deal with HP. There are also 4 neutral natures. So for example, your Onix is Hasty so his speed is higher but his defense is lower. Your Bellsprout and your Togepi have neutral natures. If you check the stats for your pokemon, you should notice for most that one stat is tinted red and the other tinted blue. Red is the increased stat, blue is the decreased stat.
The characteristic is determined by the IVs of your pokemon. IVs are Individual Values, which range from 0-31. These are all hidden values that are randomly generated when you encounter a new pokemon, sort of like their genetics. The higher the stat, the stronger it will be. Characteristic is determined by the exact value of its highest IV. So for example, your Totodile's highest IV is Attack, with a value of 2, 7, 12, 17, 22 or 27.
Keep in mind that positive nature and highest IV doesn't mean it'll be your pokemon's best stat. For example, your Onix's best stat is almost certainly its defense even though it has a negative defense nature and its characteristic tells us that its highest IV'd stat is HP.
Try not to worry about IVs or natures. They are only important if you are going to play competitively, and it's incredibly difficult to get perfect pokemon prior to Pokemon XY (where it is easier, though still tedious -- lots of breeding).
