There is usually more than one way to organize a complex subject, and this is as true for English grammar as for any other challenging study. Verbs especially have many moving parts, and without a consistent terminology, this particular department of English grammar can become unnecessarily confusing, especially when we are trying to understand verb tense.
First, it’s essential to understand the difference between a finite verb and an infinitive. Verbs express an action (she studies French) or a state of being (she is almost fluent), and when they assert action or state about a specific subject at a specific time, that form of the verb is called finite, meaning specific. Not every verb we read does this. In the sentence she wants to go to France next year, the verb wants is finite because it points to a specific subject (she) and to a specific time, the present moment. The verb to go also expresses an action, but that idea is not grammatically connected to a subject: the sentence does not say that she goes to France next year. We understand, of course, that what the subject she wants is to go to France, but we don’t come to that understanding grammatically; we know it as a logical result of the grammar. The phrase to go, therefore, is called an infinitive, the unspecific form of a verb because it is not connected grammatically to a subject somewhere in real time.
When we learn, therefore, that every sentence has a verb (either expressed or assumed), what is meant in fact is that every sentence (better, every clause) has a finite verb. That, then, puts us in a position to understand next what are called the five properties of a finite verb. A property (the word is connected with the adjective proper, meaning what is one’s own) is something that makes something what it is, and so we make a finite verb from an infinitive by applying to the infinitive the five properties (all of them, not just one): person, number, tense, voice, and mood. From the infinitive to study, for example, I specify she, and so I have determined the first two properties of person and number (third person singular). Next, I have changed the spelling of the infinitive to indicate the third property of tense (present), and that same verb form also denotes the voice (active) and mood (indicative), the fourth and fifth properties. That’s all quite specific, and that is exactly what a finite verb is meant to be.
We can see, then, that tense is one of the five properties of a finite verb. That should help us if we’re trying to learn or review the tenses in English, because not every grammar book describes the tenses in English the same way. In some presentations, for example, you’ll find things called the past descriptive tense (she was studying French) or a present conditional tense (she would like to study French), and this terminology results in a great number of so-called tenses, making the subject unnecessarily complicated. There are six tenses in English, neatly divided into two groups, simple and perfect. We begin with the mental reality we all know, that there is a present, past, and future, and then we simply put those same three ideas under two headings, simple and perfect. So the six (and only six) tenses in English are the simple present, simple past, simple future; and the present perfect, past perfect, and future perfect.
To speak of a present conditional tense, then, is to confuse the property of tense (present) with a function of a mood (the conditional use of the subjunctive). Likewise, to call something a past descriptive tense is to mix a property (tense) with yet another verbal feature called aspect (the descriptive function of the progressive aspect). All of this terminology crosses wires and produces a flash of confusion and a superabundance of tense forms. Better, I think, to apply the rule of Occam’s razor and keep things to a minimum and in its place. That way we can cut methodically through a field that has become wildly overgrown.