Learn more about Grammar:
Adjectives: An Easy Guide with ExamplesAdverbial Clauses: What Are They?AdverbsAnalogy: Definition & Meaning (with Examples)ArticlesBad AdverbsClauses: Definition, Meaning, and How to Use ThemConjunctionsCoordinating Conjunctions: What Are They and When Should You Use Them?Dangling ModifiersDeclarative Sentence: Examples + MeaningExaggerationHomophones: Definition and ExamplesHow to Use Subordinating ConjunctionsInfinitivesInterjections: Definition, Meaning, and ExamplesIntransitive Verb: Definition, Meaning, and ExamplesNounsParticiples PluralsPrepositional Phrase: What Is It & How to UsePrepositionsSplit Infinitive: The Complete Guide (with Examples)Subordinate Clause: Definition, Types, and ExamplesThe Complete Guide to Transitive VerbsTransitions: A Complete Guide (with 100+ Examples)Types of VerbsVerbsWhat is a Pronoun? Rules and ExamplesWhat Is Symbolism in Writing?Word ClassesWhy should you not overuse "could"?

Could is often overused or misused. The correct use of could indicates possibility. It means something might happen.
The election campaign could get ugly this year.
In many instances, people use could when they actually mean will, which is a more definitive word.
She could go to the store and buy one for herself.
This has a completely different meaning when you say:
She will go to the store and buy one for herself.
Only use could if you're describing truly conditional situations, or deliberately trying to be vague. If you're describing something which is definitely going to happen, use will.